Question: Simplify the following expression: $r = \dfrac{3}{8x} + \dfrac{3}{4x}$
Solution: In order to add expressions, they must have a common denominator. The smallest common denominator is the least common multiple of $8x$ and $4x$ $\lcm(8x, 4x) = 8x$ $ r = \dfrac{1}{1} \cdot \dfrac{3}{8x} + \dfrac{2}{2} \cdot \dfrac{3}{4x} $ $r = \dfrac{3}{8x} + \dfrac{6}{8x}$ $r = \dfrac{3 +6}{8x}$ $r = \dfrac{9}{8x}$